CBD on its own did nothing for acute back pain, but THC plus CBD eased migraine

Low back pain and migraine are among the biggest contributors to disability worldwide, and cannabis-based products are being marketed for both with growing enthusiasm. Yet the therapeutic value of these products for any specific condition has remained uncertain, partly because the word cannabinoids covers a very wide family: isolated CBD, synthetic drugs such as nabilone, vaporised cannabis, and standardised plant extracts. Whether any of them help, and for which type of pain, matters to a large number of people currently spending money on them. This review set out to answer the question condition by condition rather than treating cannabis as one medicine.

The authors searched electronic databases, trial registries and supplementary sources for double-blind randomised trials in adults testing cannabinoid-based interventions for low back pain, migraine or medication-overuse headache. Five trials with 1,072 participants in total met the inclusion criteria. Each study was assessed for risk of bias, the findings were synthesised narratively rather than statistically pooled, and the certainty of the evidence was formally graded. The interventions spanned isolated cannabidiol, the synthetic cannabinoid nabilone, vaporised THC and CBD combinations, and a standardised full-spectrum cannabis extract called VER-01.

For acute low back pain, a single 400-mg oral dose of isolated CBD was not superior to placebo. For acute migraine, vaporised THC plus CBD improved pain relief at 2 hours, pain freedom and freedom from the most bothersome symptom, with benefits on selected outcomes sustained through 24 to 48 hours; a CBD-dominant formulation showed no clear benefit. Nabilone showed favourable but very uncertain signals in medication-overuse headache and chronic musculoskeletal pain, while VER-01 improved pain intensity, disability, sleep quality and patient-reported outcomes in chronic low back pain. THC-containing inhaled products were associated with more psychoactive side effects and may have let participants work out what they were taking.

The overall message cuts against the idea of cannabis as a single painkiller: the review found no class-wide effect, with efficacy depending on the condition, the formulation, the route of administration and the cannabinoid mix. The authors rated the evidence for vaporised THC plus CBD in acute migraine and for VER-01 in chronic low back pain as moderate certainty, while evidence for single-dose oral CBD and for nabilone remains very uncertain. They call for larger, independently replicated trials using standardised formulations, active placebos when THC is involved, and studies of repeated use across multiple migraine attacks with longer-term safety data.

If you have been treating cannabis or CBD as one product with one effect, this review is a reason to stop. The formulation and the condition both matter: the CBD-only approach most readily available in shops did not beat placebo for acute back pain in the one trial that tested it, while the formulations with clearer signals contained THC, which brought more psychoactive side effects. None of this is a recommendation to use or avoid any product, but it is a reason to be sceptical of blanket pain-relief claims and to notice exactly what a product contains.